This invention relates to chlorination or chlorosulfonation of olefin polymers. In particular, this invention relates to a process for preparation of chlorinated or chlorosulfonated olefin polymers in suspension in perfluorinated alkane, perfluorinated ether, or perfluorinated trialkyl amine media.
Chlorinated and chlorosulfonated olefin homopolymers and copolymers are well-known compositions useful as elastomers, coatings, adhesives, and inks. The chlorinated polymers are prepared on a commercial scale by reaction of chlorine with olefin polymers in either solution or aqueous suspension, while the chlorosulfonated analogues are prepared by reaction of olefin polymers with chlorine and sulfuryl chloride or sulfur dioxide in solution. Reactive extrusion and solventless processes have also been disclosed, for example in U.S. Pat. No. 3,347,835 and in U.S. Pat. No. 4,554,326. In addition, chlorination and chlorosulfonation of solvent-swollen ethylene polymers in fluids consisting of fluorocarbons having 1-4 carbon atoms has been disclosed in British Patent 1,325,579.
Each of these prior art processes has disadvantages. Specifically, solution processes require large volumes of organic solvents, generally chlorinated solvents such as carbon tetrachloride, which must be recovered and recycled. For example, hydrofluorocarbon solvents undergo appreciable chlorination resulting in the production of undesirable chlorofluorocarbons. In addition, due to the environmental hazards associated with these halogenated materials, stringent control of emissions and substantial investments in pollution control equipment are necessary. Aqueous suspension processes, on the other hand, cannot be used for preparation of chlorosulfonated olefin polymers. Further, it is necessary to employ surface active agents during aqueous suspension chlorination processes to prevent agglomeration. The presence of such agents can have deleterious effects on the physical properties of the polymeric products. Reactive extrusion processes are not attractive because they are either limited to production of compositions containing low levels of chlorine, e.g. as disclosed in U.S. Pat. No. 4,554,326, or they are not adaptable for use on a commercial scale without major modification, see for example U.S. Pat. No. 3,347,835. Solventless processes are also not adapted to commercial scale exploitation. Finally, the process disclosed in British Patent 1,325,579, wherein fluorocarbon-swollen ethylene polymers are chlorinated or chlorosulfonated is unsuitable for preparation of a significant number of chlorinated ethylene copolymer resin types, in particular copolymers of vinyl acetate and methacrylic acid, because the surface tack of these polymers causes severe agglomeration during chlorination. In addition, these materials dissolve a portion of the chlorinated resin products resulting in sticky particle surfaces and additional isolation steps.
Thus there remains a need in the art for a process which allows production of a broad spectrum of chlorinated and chlorosulfonated olefin polymers, is economical on a commercial scale, yet does not require the use of large quantities of chlorinated solvents.